Ensure we never remove the style attribute when syncing it from CSSOM.

third_party/WebKit/LayoutTests/editing/execCommand/script-tests/toggle-style-2.js

 description("Test to make sure we remove span tags with no attributes if we removed the last attribute.")
 
 var testContainer = document.createElement("div");
 testContainer.contentEditable = true;
 document.body.appendChild(testContainer);
 
 function testSingleToggle(toggleCommand, initialContents, expectedContents)
 {
     testContainer.innerHTML = initialContents;
     window.getSelection().selectAllChildren(testContainer);
@@ skipping 12 matching lines @@
     document.execCommand(toggleCommand, false, null);
     document.execCommand(toggleCommand, false, null);
     if (testContainer.innerHTML === expectedContents) {
         testPassed("two " + toggleCommand + " commands converted " + initialContents + " to " + expectedContents);
     } else {
         testFailed("two " + toggleCommand + " commands converted " + initialContents + " to " + testContainer.innerHTML + ", expected " + expectedContents);
     }
 }
 
 testSingleToggle("underline", "test", "<u>test</u>");
-testSingleToggle("underline", "<u><b><strike>test</strike></b></u>", "<b><strike>test</strike></b>");
+testSingleToggle("underline", "<u><b><strike>test</strike></b></u>", "<b style=\"\"><strike style=\"\">test</strike></b>");
 testDoubleToggle("underline", "test", "test");
 testSingleToggle("strikethrough", "test", "<strike>test</strike>");
 testSingleToggle("strikethrough", "<u><b><strike>test</strike></b></u>", "<u><b>test</b></u>");
 testDoubleToggle("strikethrough", "test", "test");
 
 testSingleToggle("strikethrough", "<u>test</u>", "<u><strike>test</strike></u>");
 testSingleToggle("underline", "<strike>test</strike>", "<u><strike>test</strike></u>");
 
 testSingleToggle("strikethrough", '<span style="text-decoration: overline;">test</span>', '<span style="text-decoration-line: overline;"><strike>test</strike></span>');
 testSingleToggle("underline", '<span style="text-decoration: overline;">test</span>', '<span style="text-decoration-line: overline;"><u>test</u></span>');
 
 document.body.removeChild(testContainer);
 
 var successfullyParsed = true;